Too faint and quasi-stellar, in my opinion. As interacting pair to shot, I would suggest NGC 4656/57 (Hockey Stick galaxy) in Canes Venatici; the field maybe might cover also the nearby and former interacting NGC 4631 (Whale galaxy). The issues with subs should be the same like in the Needle galaxy, though. This shot should be very similar to that.

As interacting pair to shot, I would suggest NGC 4656/57 (Hockey Stick galaxy) in Canes Venatici; the field maybe might cover also the nearby and former interacting NGC 4631 (Whale galaxy).

Hockey Stick and Whale galaxy are definitely on my todo list. They should fit on one image, if I remember correctly. Still, I'm hesitating to try them with my old mount, as an upgrade to an EQ6 is becoming more and more tangible .

What I find remarkable apart from the correct spacial orientations and the proper opposite winding senses, is that the colors of both galaxies do match pretty well! This is not accidental, of course. The computer calculates the global galaxy color from the catalogued B-V color index: B-V near 1.0 gives the orange-brown color as in M 81, while B-V ~ 0.3 <<1 gives a mostly bluish appearance like in M 82...

Indeed, it's amazing how accurate the renderings from catalog data can be!

While the Hubble images are in their own league, at least the colors in my own shot are not totally off, I think

Grüße,Steffen

Indeed, Steffen, I had forgotten about this great shot of yours earlier on. The color rendering is surprisingly good, I think. The displayed photos of galaxies, globulars etc. often show dramatically different colors. This is mostly due to the fact that in these cases "raw" color profiles are used that are very far from the standardized ones used in color-management (sRGB,...).

My Celestron 8" (f:10) was far more expensive a long time ago. Being a physicist, I could not resist at the time to measure the shape of the 8" Schmidt corrector by means of laser interferometry. The shape was confirmed to be pretty bad, and after some tiring argumentation they gave me a brand new C8 after 10 years of use! The deal was that I never complain again The spherical aberration was better corrected but Coma was worse...

If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.

If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.

The internal SCT design is that. The difference is the use of ED glass for the internal coma corrector (Extralow Dispersion, HD in Celestron's fashion). This variety of exotic glasses is used for the apochromatic refractors, either for visual or astrophotography. This glass in doublets - or better in triplets and up - virtually eliminate the chromatic aberration.

If I correctly remember, the "Coma corrector" used to be a simple Achromat (doublet) near the focal plane. While it was said to reduce the Coma somewhat, it tends to introduce pretty bad color seams, since near the focal plane the rays approach under a pretty big angle. Achromats can eliminate color in such cases only poorly.

The internal SCT design is that. The difference is the use of ED glass for the internal coma corrector (Extralow Dispersion, HD in Celestron's fashion). This variety of exotic glasses is used for the apochromatic refractors, either for visual or astrophotography. This glass in doublets - or better in triplets and up - virtually eliminate the chromatic aberration.

Makes sense, but when I bought my C8 these more fancy options were not offered yet.

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